If you had to use a commuting bicycle in a race, you would probably set about removing the kickstand, fenders, racks and lights to make the thing as fast and efficient as possible. When engineers at Houston's Rice University are developing small, fast, energy-efficient chips for use in devices like hearing aids, it turns out they do pretty much the same thing. The removal of portions of circuits that aren't essential to the task at hand is known as "probabilistic pruning," and it results in chips that are twice as fast, use half the power, and are half the size of conventional chips.
"I believe this is the first time someone has taken an integrated circuit and said, 'Let's get rid of the part that we don't need,'" said principal investigator Krishna Palem, a Professor of Computing at Rice. "What we've shown is that we can boost performance and cut energy use simultaneously if we prune the unnecessary portions of the digital application-specific integrated circuits that are typically used in hearing aids, cameras and other multimedia devices."
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There is a cost for those improvements, however – the pruned chips gain an error magnitude of 8 percent. The researchers are OK with that, though. The chips are designed to allow for the probability of errors, and to limit which calculations cause them. Even with that additional 8 percent error magnitude, they should reportedly still be fine for hearing aids and similar devices, which the team states can tolerate error magnitudes as high as 10 percent.
Pruned and traditional chips that were created together will be presented in a side-by-side comparison at this week's DATE11 microelectronics conference in Grenoble, France. While the pruned chip is expected to perform at twice the speed and using half the power of the regular chip, Palem has even higher hopes for a hearing aid-specific chip that he is about to design – four to five times more run time on a set of batteries.
Probabilistic pruning stands in sharp contrast to the self-monitoring, self-repairing chips that we just featured in Gizmag. In that case, researchers have added cores to chips, so that tasks allocated to cores that are found to be defective can be reassigned to functioning ones.